Allergic disorders are a major global health concern affecting 150 million people worldwide. Recently, epithelial cells have emerged as central participants in the pathogenesis of allergic inflammation. Defining the key epithelial drivers of the development, persistence, and progression of allergic inflammation is the focus of this application. Although epithelial cells are increasingly recognized as critical participants in the initiation and propagation of allergic inflammation, therapies that specifically target the epithelium are lacking. There are substantial gaps in understanding the mechanisms by which epithelial pathways converge to promote allergic inflammation that must be filled before interventions can be designed. Our U19 AADCRC proposal is designed to help fill this critical knowledge gap. We are uniquely poised for the proposed studies because of resources and collaborations that we have developed over the past 2 decades. Through the synergistic projects, we will explore the immunological mechanisms, which underpin initiation, persistence, and progression of allergic disease and provide novel insights into a key unanswered question in the allergy field: Why is allergic inflammation restricted to one tissue in some cases, while it progresses to involve additional tissues in other individuals? The projects are: Project 1 ? To elucidate endotypes of AD that are predictive of progression to asthma and dissect the mechanistic basis of the contribution of epithelial kinesin family member 3A (KIF3A) to allergic inflammation and disease persistence/progression. Project 2 ? To determine how protease/protease inhibitor imbalance promotes allergic inflammation - dissect the mechanistic basis by which the epithelial-derived protease inhibitor serine protease inhibitor Kazal-type 7 (SPINK7) promotes allergic inflammation . Project 3 ? To dissect the mechanisms by which a newly described population of mucosal mast cells (MMC9) that make large amounts of IL-9, IL-13, and mast cell protease 1 (MCPt-1) develops and amplifies allergic inflammation to promote progression of AD to allergic asthma. Investigations in this domain will ultimately provide a road map for primary or secondary prevention of allergic disease. As such, this proposal is highly aligned with the stated programmatic priorities in the RFA-AI-15-032.